The tiny spring peeper is never much more than one inch in size. It is found throughout Illinois and can be recognized by the dark “X” mark on its back and the dark line between its eyes. The spring peeper is usually tan or brown with a pinkish tint. This smallest treefrog is rarely seen except when breeding from early March to early June. It lives in moist, brushy woodlands and lays its eggs in woodland ponds. During the day it calls from the branches of trees or from under leaves on the forest floor. At night, its piping, clear whistle can be heard from the edge of the water or from plants over the water.